Electronically controlled stage lights may use a computer to control the output of a digitally, pixel level controllable, lighting projector. For example, a processor may produce a digital output that controls a digital micromirror based processing device, such as a DLP projector.
An image is used as the control for the projector. Different lighting effects may be carried out on the image which is used to drive the projector to produce the lighting output. Many of the image operations which were previously carried out by physical components, such as lenses, cut gobos, and the like may be effected by a digital electronic technique which simulates the effect of those physical components. Other effects are described in U.S. Pat. Nos. 5,828,485; 6,057,958, and others, and may include image rotation, image movement, or other image manipulation operations.
One such effect is a blur effect which has been traditionally carried out by a Gaussian type lens which blurs the image. The traditional thinking is that a digital version of the Gaussian blur would involve taking the original image pixel by pixel, and calculating a blurred value for each pixel in the blurred image based on the values of the pixels that surround the equivalent pixel in the source image.
Conventional Gaussian blurring would take the area of a blur window used in a calculation specified as a circle containing the source pixel, centered on the destination pixel, as shown in FIG. 1. Each of the source pixels would then be weighted by a value related to the radial distance from the pixel to the center of the circle, according to a Gaussian weighting. Pixels closest to the circle's center will have a greater weighting than pixels nearest the edge. A conventional Gaussian weighting is shown in FIG. 2. The weighting of the Gaussian would therefore weigh various pixels by different amounts.